The purpose of this three-part project is to examine the functional organization of neurons in the motor cortex. Rats have been choosen as the primary experimental animals since they are readily available, easy to condition, and have small lissencephalic brains. (1) Neuroanatomical and neurophysiological techniques will be employed to characterize the first motor cortex (MI) in rats and determine the connectional relationships of MI with other neural structures. (2) We will record from several classes of projection neurons in the forelimb area of MI cortex in awake, behaving rats. In these experiments, the relationship of the neuronal activity to motor output will be examined for each identified class of neurons, e.g. corticospinal cells and corticostriatal cells. (3) Intracellular recording will be combined with intracelluluar injection of a tracer, horseradish peroxidase, to visualize the distribution of neuronal processes, in different layers of MI cortex, of identified projection neurons. These experiments are directed toward an understanding of information processing within the motor cortex, in particular the mechanisms of the input-output functions of the motor cortex.